1. Field of the Invention
This invention relates to an electrolytic cell for generation of chlorine and an alkali for introduction into a swimming pool, and to a method of operating such a cell.
2. Description of the Prior Art
There have been a number of proposals for chlorinating the water in a swimming pool, or some other body of water, by generating chlorine by the electrolysis of salt water (brine). An anode and a cathode are disposed, in an anode chamber and a cathode chamber, respectively, and are separated by a wall or dam which wall or dam has an ion-permeable membrane disposed therein. The electrolysis of the brine causes disassociation of sodium and chlorine ions, thereby generating chlorine gas in the anode chamber and sodium ions which pass through the membrane into the cathode chamber. In the cathode chamber, the sodium ions combine with the water therein to form sodium hydroxide (NaOH). The sodium hydroxide is formed due to the disassociation of the water in the cathode chamber into hydrogen ions H(+) and hydroxyl ions OH(-). The hydrogen ions combine with electrons from the cathode to produce hydrogen gas, which gas escapes from the liquid. The surplus hydroxyl ions combine with the sodium ions that have passed through the membrane to form sodium hydroxide. As the sodium ions pass through the membrane and into the cathode chamber to form the catholyte, sodium hydroxide, the volume of the catholyte increases. The prior art teaches that the catholyte may be disposed of either by introduction into the water of the swimming pool, or by drainage.
Patents exemplifying the above-noted state of the art include Murray Pat. No. 3,223,242 which uses an electrolytic cell for the electrolysis of a saline solution, which electrolysis generates chlorine which is delivered to a venturi which is disposed in a conduit between a pump and a swimming pool inlet. Richards et. al. Pat. No. 3,563,879 provides a cylindrical electrolytic chlorine generator having a closed, pressurized cell and in which a solution of sodium hydroxide and brine collects at the bottom of the unit, which solution is discharged through a conduit connected with a pipe leading to the swimming pool. Kirkham et. al. Pat. No. 3,669,857 provides a cell of the membrane type for the electrolysis of brine, wherein chlorine and brine are delivered to one conduit, by a bubble action, to a feed pipe to the swimming pool, and wherein sodium hydroxide and hydrogen gas are delivered through another conduit to the feed pipe. Kirkham provides a brine tank, from which brine is pumped through a filter and a medium to continuously supply the anode chamber, and a time controlled valve which is used to drain excess catholyte.
Tighe et. al Pat. No. 4,129,493 utilizes an electrolytic cell having a cation exchange membrane. Deionized water is delivered to the cathode chamber and saturated brine made from deionized water is delivered to the anode chamber. The products of electrolysis, including sodium hydroxide, hydrogen gas and water generated in the catholyte chamber and chlorine and oxygen generated in the anolyte chamber, are combined to produce sodium hypochlorite. Richards Pat. No. 4,439,295 introduces water into an electrolytic cell from the swimming pool circulator pump, and generated chlorine gas and sodium hydroxide are delivered to water returning to the swimming pool. Yates Pat. No. 4,229,272 discloses an electrolytic cell wherein chlorine and hydrogen gases are delivered to a gas feed apparatus for delivery to a swimming pool feed conduit. Yates makes no disclosure concerning the delivery of sodium hydroxide to the swimming pool.
Sweeney Pat. No. 4,256,552 provides an electrolytic chlorine generator which generates and introduces chlorine gas and hydrogen gas into a swimming pool feed pipe. Sweeney Pat. No. 4,248,681 additionally provides for the production of chlorine dioxide and mixtures of chlorine dioxide and chlorine. Sweeney Pat. No. 4,308,117 is characterized by an electrolytic cell having two membranes.
Other patents of interest include Olivier Pat. No. 4,411,759; Murray et. al. Pat. No. 3,361,663; McCallum Pat. No. 4,085,028; Coker et. al. Pat. No. 4,214,958; Kosarek Pat. No. 4,361,471; Themy Pat. No. 4,171,256 and Yates Pat. No. 4,097,356.
The known electrolytic cell chlorine generators are deficient in a number of specifics. Some do not provide for the utilization of the caustic produced by the electrolytic cell, while some utilize an unsafe pressurized cell. Many introduce into the swimming pool water all products of the electrolytic cell or more than the desired products, and are of complex construction. These devices require such items as deionizers, multiple pumps, solenoid operated valves, gas mixing stages, and may require the introduction of pool water from the circulator pump into the electrolytic cell. Moreover, the known electrolytic cells, where used in combination with swimming pools, do not provide for an interrelationship between the electrochemical action of the cell and the products produced and the alkalinity of the swimming pool water.